PHOENIX -- It's the last line of defense for wildland firefighters -- a thin, mylar-like cocoon designed to reflect heat and hopefully save lives.
The 19 firefighters killed while fighting the Yarnell Hill Fire Sunday reportedly deployed their emergency shelters as the wind-whipped flames came at them, but it's still not clear exactly what happened out there. Eighteen of those firefighters were part of Prescott's Granite Mountain Hotshots.
"The shelters are meant as a very last resort, something that we train for, but we never envision it happening" Prescott Fire Department spokesman Wade Ward told 3TV's Crystal Cruz Monday morning, just hours after the men were killed. "We're just trying to figure this all out, wrap our heads around it."
Lance Frawley of the Apache Junction Fire Department, who knew and worked with the Granite Mountain Hotshots, demonstrated how the emergency fire shelters are deployed. It takes only seconds and is something wildland firefighters practice over and over until the movements are almost second nature.
"We don’t want to be put in that situation where we're having to deploy these," Frawley said. "But as a very last option, when we've exhausted all other opportunities, we're going to go ahead and deploy this and it's going to give us our best chance for survival."
Video from a Cronkite New Service Report shows members of the Granite Mountain Hotshots practicing the same procedure Frawley showed 3TV's Javier Soto.
When it comes to deploying an emergency fire shelter, timing is key. The heat inside can be suffocating, so a firefighter does not want to deploy it too soon. If he waits too long, however, the fire can be on top of him before he is safely cocooned.
As the fire bears down, the firefighter wants to be as low as possible, back flat on the ground, even in a depression if at all possible. He also wants to be sure to keep his feet to the approaching flames.
"Under certain conditions there's usually only sometimes a 50 percent chance that they survive," Prescott Fire Chief Dan Fraijo told The Associated Press. "It's an extreme measure that's taken under the absolute worst conditions."
The emergency shelter is meant to reflect 95 percent of the radiant heat of the flames as they pass over. It's not designed to withstand stationary flames.
"The one thing that it doesn't really do well is direct flame contact," Frawley explained.
If fire burns the shelter for any length of time, the glue that holds it together will eventually delaminate, causing the shelter to come apart.
Some of the fallen firefighters reportedly were found inside their shelters.
At this point, it's believed that the wind caused the massive flames to suddenly change direction and trap the 19 firefighters. An investigation is under way.